Hot-air furnace



Sept. 24, 1946. Y I J. 0. MILES 2,408,037

HOT AIR FURNACE Filed July 24, 1945 4 Sheets-Sheet 1 INVENTORQ Y Jjne3(ZN/4e:

BY 'l lau v 771 004 pt 24,1945; J. c. muss 2,403,037:

H01: AIR FURNACE Filed July 24, 1945 4 Sheets-Sheet 2 v..'... wcvwww Jrl7 'INVENTOR. 7414:: C Hue:

"ew-zmyhm' Irrakdlrl Filed July 24, 1945.

J. c; MILES HOT AIR F-URNACE 4 Sheets-Sheet 5 Ema: (WY/e:

Sept, 24, 1 946.

J.'C. MILES HOT AIR FURNACE Filed July 24, 1945 4 Shets-Sheet 4INVENTOR. Jinn C. Mmes' BY m. 'fmpm Patented Sept. 24 1946 OFFICEHOT-AIR FURNACE James 0. Miles, Cleveland, Ohio I Application July 24,1943, Serial No. 496,015 I This invention relates to heating devices andmore particularly to a coal or oil burning Warm air furnace of a typesuitable for use in large private dwellings, apartment houses, or ingarages or factories, airplane hangers, andthe like.

There is .a great demand for an efiicient hot air furnace that mayoperate on either coal, gas, or oil as fuel, and that is suitable forheating lar installations, such as factories, and airplane hangers,where the ceiling is comparatively .high, and Where the presence ofmachinery or .equipmentmakes it diflicult to utilize steam or hot waterradiators or pipes to advantage. As an attempted method of solving theproblem of heating such installations, the practice has been to employhot air heating furnaces with outlet funnels that are swivelly mountedat the top of the furnace and are adapted to direct the heated air into.any predetermined direction. By mounting such units at spaced intervalsalong the wall of a large building; quick responseto a heating demandmay be obtained and heat maybe supplied to any localized part of thebuilding onto the entire building as, desired.-Thus, for example, heatmay be directed immediatelyagainst the engines of an airplane to warmthem prior to a take-off under low temperature conditions.-

Anobject of. thepresent invention is to construct a furnace suitableasaforesaid, and which will possess a maximum amount of heating surfaceand fire travel with a minimum amount of floor space, and which willhavea high degree of operating efiiciency, as measured by the ratio ofheat output to heat input, which is comparatively small and compact, andwhich can be made principally of stampings. The invention furthercontemplates 3. construction-which may readily be furnished in varioussizes in an expeditious manner. Other features of the invention willbecome apparent in the following description and in the accompanyingdrawings.

In the draWings,.F-ig. 1 is a side'view of a furnace embodying thepresent invention; Fig. 2 is a section taken on the plane indicated bythe line 2-2 in Fig. 1; Fig. 3 is 'a section taken on the planeindicated by the line 33 in Fig. 2; Fig. 4 isa section taken on the line4-4 in Fig. 3, and Figs. 5 and 6 are sections taken on thecorrespondingly numbered lines in Fig. 4. The present inventionconstitutes a furnace heating chamber and ablower constructed as aunitary structure. Tothis end, the'unit has a housing which forms abox-like structure having a front Wall l0, arear wall! I, side walls 12and a top wall l3. The furnace or combustion cham- 5 Claims. (01.126104) ber l6 extend from the front to the back wall, but is spacedinwardly from the side walls of the housing and is provided with its ownside walls l5, which preferably are curved plates that extend from thefront to the rear Wall of the housing and that cooperate to provide anarch shaped roof for the furnace chamber. Portions of the plates l5 maybe bentinwardly as at H, to provide supports for afurnace lining H3, atabout the level of the grate bars |9. The openings left in the sidewalls by the deformation thereof provide apertures for air to enter thefurnace chamber beneath the grate bars for the purpose of supportingcombustion within the furnace. A cage may extend along the outer side ofeach wall l5 for covering each aperture 20, and each cage has an opening26 therein that is adapted to be closed by a damper 21, that is pivotedfor swinging movementinside of each cage. 7 v

The heating chamber for the unit'is the space disposed between thehousing walls and the furnace chamber walls l5. Preferably the housingside walls l2 terminate short of the floor upon which the unit rests,while plates 30 extend from the lower edges thereof to the plates l5 toform the bottom of the heatingchamber. Suitable apertures in the plates,30 may receive thedischarge spouts 3i ofblowers, indicated in generalat 32, that are mountedon oppositesides of the unit and beneath thebottom plates 30.- Two blowers are illustrated on each side of the unit,and each is adapted to be operated by a motor 35 that is disposed at therear'of the unit. I

As shown in Fig. '2, the side walls I 5 are spaced apart attheirupperedges, wherefore the top of the furnace chamber merges with a smokechamber that extends from the front to the rear walls In and II, andthat has sidewalls 31 and 'a top wall 38. A partition 39 divides the'smokecha'mber into upper and lower compartments and has spacedapertures 40 therein which are adapted to be selectively opened orclosed by a damper, preferably in the form of 'a slidable plate 4 I thatmay be controlled by an operating arm 42 as shown in Fig. 3. The damperhas apertures 43 which are adapted to register with the partitionapertures 40, whenever the damper is moved to the necessary extent. InFig. 3 the openings are out of registration, wherefore, theheatedproducts of combustion :cannot flow directly into the uppercompartment of the smoke chamber and thence .out the, flue 45, but areforced to flow in a tortuous path through-banks of fire'tubes that aredisposed within the heating chamber and between the side walls l2 and[5, respectively.

The fire tubes shown in Figs. 1 and 2 are disposed in close proximity toeach other, and each comprises two metal stampings 46 and 41 that arewelded together at their peripheral edges, and are so formed as toprovide a tubular passageway that is preferably oval in cross section.Each tube thus formed comprises. a long curving U the legs of which. areshaped substantially complementary to the side walls l of the furnacechamber, while the two open upper ends thereof are shown incommunication with the smoke chamber at points above and below thepartition 39, respectively. Communication between the tubes; and smokechamber is provided by suitable openings in the side wall 31 foraccommodating the ends of the tubes. Each tube extends downwardly forsubstantially the entire length of the combustion chamber, thuspermitting the maximum amount of' heat to be transferred from theburning fuel to the circulating air which is introduced through thebottom walls of the heating chamber, by means of the blowers 32. Part ofthe air forced into the heating chamber may also be forced into thefurnace ash pit for supporting combustion, through the apertures 26 and20; it being understood that the pressure of the air is sufficient toswing the dampers 21 to open position whenever the blowers are inoperation.

A furnace madeaccording to the present invention has resulted ina ratioof heating surface to the grate area of 30 to l, and the same ratio canbe maintained notwithstanding the number of tubes which may be utilizedin the furnace. The space required to add more tubes automaticallyincreases the area of the grate in an amount to maintain the same ratioof 30 to 1.

As will be observed in Fig. 3, the opening 50 for the entrance ofproducts of combustion into each fire box tube is larger than thedischarge opening 5|, wherefore the velocity of the gas isundi'mi'nished as it cools during its passage through the tubes.Additionally, the cross secti'onal shape of each fire tube is alteredintermediate the points of inlet and outlet, and preferably in the outerleg, so as to defi'ect the air from the blowers toward the hottestregions of the tubes and furnace walls. This may best be observed inFig; 2, wherein the region of the outer leg of each tube is narrowerfrom the point 52 to the point 53 than it is between the point 53 andthe outlet 5|. As shown in Fig. 3; the outlet opening 5| is ellipticalin shape and the major axis extends vertically. That condition prevailsbetween the points 5| and 53, but between the points 52 and 53 the majoraxis and minor axis are transposed, thusimparting greater width to thetube as may be observed in Fig. 1.. The outer legs of the tubes,therefore, cooperate'to provide, in effect, a curved battle which tendsto confine the major portion of air against the hottest portions of thetubes and furnace walls;

To obtain a better degree of contact between the air to be heated. andthe hottest portions of the furnace, I may utilize baffles 69 whichpreferably comprise corrugated curved plates that lie between the curvedportions of each tube and extend from the point 52 to the region of thepoint 53. Each baiile may extendfroin one bank of tubes to the other, asshown in Figs. 5 and 6', and each may have a fin 6| that is preferablycorrugated and extends from the mid-portion of the baffle to the wall ofthe combustion chamber. The fins preferably abut the combus tion chamberwall so as to conduct heat, by radiation, therefrom, and to transmit itto the air that flows upwardly through the heating chamber.

For convenience of cleaning, each tube is provided with an enlargedportion 55 at the base of the U for trapping non-combustible particles,and such enlarged portion is provided with a clean-out door 56 that isaccessible from the exterior wall of the housing and is detachablymounted thereon. A suitable cleanout tray 51 extends along each side ofthe housing for re ceiving the material that is removed from the tubes.

If desired, the air which is heated by the furnace may be led directlyinto conduits which convey it to various parts of the building, or, asillustrated in Fig. 1, the air may enter funnels 10 that are swivellymounted on the top wall [3 of the housing. Thus, the funnels may beturned in any desired direction for the purpose of obtaining intenseheat in a localized zone, or may be turned in diverse directions toeffect a heating of a general zone.

The furnace unit made in accordance with the present invention possessesa high degree of economy of manufacture in that most of the parts may bemade from stampings, and in that a high degree of output may be obtainedfrom a furnace that occupies a comparatively small space. Theutilization of curved fire tubes which are shaped to correspond to theslope of the furnace walls; and the provision of such tubes in banks aidin attaining compactness, and likewise aids in procuring a high degreeof output for a given input. An additional feature of the presentinvention is the fact that the furnace may be made of any desired lengthmerely by increasing the number of tubes, without in any way alteringthe method of operation or changing the features which account for thehigh degree of operating efficiency.

I claim:

1. A hot air heating furnace having a body forming a combustion chamber,and having a smoke chamber superimposed thereon, a housing forming aheating chamber on both sides of the combustion chamber, the heating"chamber having an air inlet at the bottom and an air outlet at' the topthereof, a plurality of fire tubes disposed within the heating chamberand being shaped substantially complementary to the sides of thecombustion chamber, each fire tube having one end thereof incommunication with the combustion chamber and having the other endthereof in communication with the smoke chamber and extending downwardlyinto the chamber for substantially the depth of the combustion chamberand thence upwardly to communicate with the smoke chamber, and each ofsaid tubes having a cross section comprising along and a short axis, thetubes being so positioned that at the upper ends thereof. the long axisextends transversely of the furnace and adjacent the bottoms thereof thelong axis extends longitudinally of the furnace.

2. A hot air heating furnace having a body forming a combustion chamber,a; housing enclosing the same. and. forming aheating chamber, theheating chamber having an. air inlet at the bottom and an air outlet atthe topthereof, said body having. a smoke chamber disposed above thecombustion chamber, fire tubes disposed in the heating chamber on bothsides of the combustion chamber; each tubehaving one end thereof incommunication with the combustion chamber at a point adjacent the topcentral portion of the combustion chamber and having the other endthereof in communication with the smoke chamber, said fire tubesextending down into the heating chamber for substantially 'the depth ofthe combustion chamber and thence upwardly to communicate with the smokechamber so as to provide an inner and an outer leg on each tube, andeach tube having a cross-section comprising a long and a short axis, theend portions of each tube having the long axis extending transversely ofthe furnace and an intermediate portion of each tube having the longaxis extending longitudinally of the furnace.

3. A hot air heating furnace having a body forming a combustion chamber,a housing enclosing the same and forming a heating chamber, the heatingchamber having an air inlet at the bottom and an air outlet at the topthereof, the combustion chamber having side walls that converge in theupper portion of the chamber, a smoke chamber disposed above thecombustion chamber and extending longitudinally of the cen, tral regionthereof, fire tubes of generally U- shape, disposed in side-by-siderelationship with in the heating chamber and on each side of thecombustion chamber and in close proximity thereportion having the longaxis extending longitudinally of the furnace.

4. A hot air heating furnace having a body forming a combustion chamber,and a smoke chamber superimposed thereon, a housing forming a heatingchamber on opposite sides of the combustion chamber, the heating chamberhaving an air inlet at the bottom thereof and an 6 air outlet at the topthereof, a plurality of fire tubes disposed within the heating chamberon opposite sides of the combustion chamber and extending downwardlywithin the heating chamber for substantially the depth of the combustionchamber but not below the level of the grate therein, each tube beingformed to provide an outer and an inner leg and having one end thereofin communication with the combustion chamdeer and the other end thereofin communication with the smoke chamber, and each tube having across-section comprising a long and a short axis and being so positionedthat the inner leg has the long axis extending transversely of thefurnace while the outer leg has the long axis extending transversely ofthe furnace on its upper portion, but has the long axis extendinglongitudinally of the furnace on the lower portion thereof.

5. A hot air heating furnace having a body forming a combustion chamberand a smoke chamber superimposed thereon, a casing forming a heatingchamber outside the combustion chamber, the heating chamber having anair inlet at the bottom and an air outlet at the top thereof, fire tubesdisposed within the heating chamber on both sides of the combustionchamber and each having one end thereof in communication with thecombustion chamber and the other end in communication with the smokechamber, the tubes being generally U-shaped and each having one leg ofthe U in close proximity to the wall of the combustion chamber, andhaving the other leg of the U in close proximity to the inner leg, andeach of said tubes having a cross-section comprising a long and a shortaxis, the inner legs having the long axis extending transversely of thefurnace, and the outer legs having a major portion thereof with the longaxis extending longitudinally of the furnace, baflles interposed withinthe heating chamber so as to direct the flow of 'air through the heatingchamber into close proximity with the walls of the fire tubes forsubstantially the depth of the combustion chamber, the bafilescooperating with the tubes to define cellular passageways for the air inthe heating chamber.

JAMES 0. MILES.

